Technical Field
The present invention relates to particle manipulation devices, and more particularly to devices having paths and mechanisms for trapping and controlling microparticles and microorganisms as well as radiation generating electronic circuits for biasing of the microparticles.
Description of the Related Art
Point of Care (PoC) devices have increased in the interest for microfluidics-based devices. Microfluidics-based devices have the potential to perform entire biological experiments or immunological tests on a single credit card-sized or even smaller chip. PoC devices provide miniaturized laboratories for fast, inexpensive, easy to use, portable tests, such as e.g., blood sugar testing and the like.
Techniques exploiting dielectrophoretic (DEP) forces have emerged as a powerful touch-less method for cell and particle discrimination, separation, isolation or concentration, useful for sample processing. The dielectrophoretic (DEP) forces arise from interactions of field-induced charge polarization in cells or particles with field inhomogeneneity that acts to attract (or repel) cells to (or from) electric field maxima for positive (or negative) dielectrophoresis forces. An electrically polarizable object will be trapped in a region of a focused electric field. These forces depend not only on the geometrical configuration and excitation scheme of the electrode array but also on the dielectric properties of the cell or particle and of its suspending medium. The magnitude, direction and frequency dependencies of DEP responses depend on the composition, size and conductivity of both particle and medium.
DEP has been employed for the separation of live from dead yeast cells, live from dead bacteria cells, malaria-infected cells from healthy cells, and human leukemia cells from healthy blood cells. For example, the membrane of red blood cells (erythrocytes) turn very permeable to ions when they become infected by malarial parasites, resulting in the loss of internal ions to the low-conductivity suspending medium and a much lower internal conductivity as compared to healthy red blood cells.
One way to make a DEP trap is to create an electric field gradient with an arrangement of planar metallic electrodes in a channel. A form of electrode-less dielectrophoresis manipulation can be done through the use of a strongly focused beam of light, commonly known as “optical tweezers” or through a hybrid variation using photoconductive materials, the “optoelectronic tweezers”. Intensity gradients in the converging beam draw small objects, such as a colloidal particle toward the focus, such that particles can be trapped in three dimensions near the focal point. They can operate by dynamically positioning potential energy minima and maxima.
While electrodeless DEP does not need metal evaporation during the fabrication, the structure is chemically inert with no impact on cell integrity or viability, and it avoids electrolysis at metal DEP electrodes with very high electric fields; this approach requires large, expensive, energy-intensive equipment that is external to the microchip and can only be used in a laboratory setting. Other electrode-less DEP structures involve changes in the microfluidic channel geometry such as constrictions or pillars.